With very dangerous media, even the minimal ISO FE-Series leak rate can be too high. In cases like these, you can, however, use tried and tested AS-Schneider bellows valves.
To move the valve stem upwards and downwards on a leak-free basis, a multi-layer, metal bellow is used that is firmly attached on the one side to the stem and on the other side is firmly welded to the housing. This makes it impossible for the medium to escape along the valve stem.
“Technically leak-proof” properties are as follows: fully flushed, multi-layer stainless steel bellows valve, secured against twisting, and designed for 2500 operations. Moreover, bellows completely welded to stem and housing, pivoted valve tip in stellite 6 material, safety packing and available pressure classes: PN100, PN250, PN400 by request.